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Pedestal Coordinates - These are the AZ/EL spherical coordinates of the pointing vector, in
the pedestal reference system. AZ is measured clockwise (when looking down on the
antenna) from the AZ Home Position. The antenna boresight will be parallel to the frame of
the antenna at the Home Position. EL is measured up from a boresight of 0 degrees.
The AAQ calculates the pointing solutions in Pedestal Coordinates. These are the Pedestal
Coordinates that will point the antenna boresight at the Target Satellite if the Pitch and Roll are 0.0
and the Heading is exactly equal to the current heading. These are displayed in the “Target
Selection” section of the AAQRemote GUI main window as “Actual” values and are output as Sensor
Outputs.
The AAQ calculates Tilt Corrections that must be made to the pointing solution. These tilt
corrections are calculated by a “3 rotation tilt transform” using Yaw (Heading) followed by Pitch and
then Roll. The Yaw, Pitch, and Roll values used in this transform are measured during a Home
routine at power up. When these corrections are added to the “Actual” values, they become the
Pedestal Coordinates that will point the antenna boresight at the Target Satellite assuming the Pitch,
Roll, and Heading values last reported by those sensors.
This process is performed whenever the AvL antenna system is powered up or a new target
satellite/profile is selected in any AAQ GUI (AAQRemote .Net, Web Server, CIP or Handheld).
7.4.6 Acquiring the Satellite Signal
The AAQ usually acquires the Target Satellite by executing a single Azimuth (AZ) Line Scan (Azimuth
angle varied while the Elevation angle is held constant) centered on the best current Ped-AZ / Ped-
EL pointing solution. If this initial AZ Line Scan is not successful, then a raster scan is performed
automatically. This raster consists of several back-and-forth Azimuth line scans at different Elevation
angles. The AZ width, EL height, and EL step size of this scan volume are all based on user settable
configuration parameters. The AAQ acquisition scan is illustrated in Figure 7.4.6.
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